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Scientists Claim Water Evaporated From Trees Cools Global Climate

  • Sep 15, 2011

Scientists have long debated about the impact on global climate of water evaporated from vegetation. New research from Carnegie's Global Ecology department concludes that evaporated water helps cool the earth as a whole, not just the local area of evaporation, demonstrating that evaporation of water from trees and lakes could have a cooling effect on the entire atmosphere. These findings, published Sept. 14 in Environmental Research Letters, have major implications for land-use decision making.

Evaporative cooling is the process by which a local area is cooled by the energy used in the evaporation process, energy that would have otherwise heated the area's surface. It is well known that the paving over of urban areas and the clearing of forests can contribute to local warming by decreasing local evaporative cooling, but it was not understood whether this decreased evaporation would also contribute to global warming
 
The Earth has been getting warmer over at least the past several decades, primarily as a result of the emissions of carbon dioxide from the burning of coal, oil, and gas, as well as the clearing of forests. But because water vapor plays so many roles in the climate system, the global climate effects of changes in evaporation were not well understood.
 
The researchers even thought it was possible that evaporation could have a warming effect on global climate, because water vapor acts as a greenhouse gas in the atmosphere. Also, the energy taken up in evaporating water is released back into the environment when the water vapor condenses and returns to earth, mostly as rain. Globally, this cycle of evaporation and condensation moves energy around, but cannot create or destroy energy. So, evaporation cannot directly affect the global balance of energy on our planet.
 
The team led by George Ban-Weiss, formerly of Carnegie and currently at Lawrence Berkeley National Laboratory, included Carnegie's Long Cao, Julia Pongratz and Ken Caldeira, as well as Govindasamy Bala of the Indian Institute of Science in Bangalore. Using a climate model, they found that increased evaporation actually had an overall cooling effect on the global climate.
 
Increased evaporation tends to cause clouds to form low in the atmosphere, which act to reflect the sun's warming rays back out into space. This has a cooling influence.
 
"This shows us that the evaporation of water from trees and lakes in urban parks, like New York's Central Park, not only help keep our cities cool, but also helps keep the whole planet cool," Caldeira said. "Our research also shows that we need to improve our understanding of how our daily activities can drive changes in both local and global climate. That steam coming out of your tea-kettle may be helping to cool the Earth, but that cooling influence will be overwhelmed if that water was boiled by burning gas or coal."

Comments

Sun, Sep 25, 2011 Michael Ioffe Highland Park, IL, 60035

If we will change our transportation system our heat, hot water, and electricity production, we could reduce our needs for energy at least seven times. In this case wood will provide more useful energy than coal and oil product right now. Of course we could use mix of wood, natural gas and coal in environmentally friendly proportions. We could put all gases from oven, which used wood in water, to watering forests around power plants. It will be zero emission energy production. In 48 states we have 600,000,00­0 acres of forested land. 300,000,00­0 acres of land are more than enough for USA energy needs. It is possible to harvest 5 dry ton/acre, year. Average heating value of 8,000 BTU/lb(dry)or 89,596,000BTU/acre, year Consumption of energy in 2010 (projection)- 107,870,000,000,000,000 BTU / 89,596,000BTU/acre year=1,200,000,000 If our energy needs will reduce 7 times we need only 1,200,000,000/7=171,000,000 acres of forest. Changing our transportation system, electricity production, growing forests for wood energy will: 1. Make North American countries energy independent. 2. Create 100% of employment in USA, Canada and Mexico. 3. Create possibilities to fight climate change with help of these three countries. North America between Pacific, Arctic, and Atlantic oceans is influent climate from France to Japan.

Sun, Sep 25, 2011 Michael Ioffe Highland Park, IL, 60035

Reason for change: Transportation system Efficiency of engine in most cars moving by gasoline is around 30%. Efficiency of gasoline production is less than 45%. It means that real efficiency of car movement is around 13.5% If person (200 lb.) mostly alone is driving in this car (4,000 lb.) it means that efficiency of movement of this person in this car is 0.67%. Perhaps mass (m) of car is 2,000 kg, mass of driver 100 kg and speed (V) of car 65 miles per hour or 110.5 km/hour or 30.7 m/sec Kinetic energy of this car will be as follows: *** 1/2mv²=1/2 x 2100 x 30.7 x 30.7=1/2 x2100 x 942 As you can see in this case, the mass of car and its driver change the amount of kinetic energy twice more than the speed. It is less important, if we drive on strait road without stop on long distance. But usually it is traffic, or driving in city with stop on every light. We are losing energy in vain. If we will analyze situation with public transportation—cars, busses, trains, high speeds transportation situation will be even worst than for car. These types of transportation are heavier than car and Have many people aboard, which will wait few people going in and out. It will be better to move one person on small cart with weight 20 lb. moving by electricity directly from grid. It will reduce energy for transportation at least ten times. We could also reduce energy needs for moving every boat, creating forces, which will reduce underwater part of boat. Power plant The burning of fossil fuels (coal, natural gas, or petroleum) in power plant. In hot gas (gas turbine), turbines are driven directly by gases produced by the combustion of natural gas or oil. Gas turbine plants are driven by both steam and natural gas. They generate power by burning natural gas and use residual heat to generate additional electricity from steam. These plants offer efficiencies of up to 60%.” In grid we are loosing more than 7% of energy. It means 11.6% of energy of fuel. 60%-11.6%=48.4 According maximum power theorem, resistance of source of energy must be close to resistance of load. In source of energy we are loosing around 50% of energy. 48.4/2=24.2 Efficiency of load in average is less than 80%. 24.2 x0.8=19.36 Not all plant has up to 60% of efficiency. And if you will speak with Engineers from usual power plants it is common – 13% of efficiency. As you see efficiency of power plant, which is common for USA is less than 20%. If we change power plant to use as heat as electricity power wood could provide more useful energy, than right now coal, natural gas, or petroleum. Smoke from coal, natural gas, or petroleum is toxic for forests. Smoke from wood we could put in water to watering forests, surrounding power plants. Together with ash it will be the best nutrition to grow trees. Let compare wood and coal by energy capacity: 1 ton coal = 16,200,000 to 26,000,000 Btu 1 ton wood = 9,000,000 to 17,000,000 Btu

Sun, Sep 25, 2011 Michael Ioffe Highland Park, IL, 60035

Main mistakes of science of climate change are mixing all greenhouse gases together and make all of them equally responsible for climate change. It is especially wrong for water vapor, which together with others properties of water actually cooling earth atmosphere. Water evaporated from all surfaces of oceans, seas, lakes, rivers, Water evaporated from leaves of any plants. Water evaporated from any wet surfaces. In atmosphere we always see dynamic processes of evaporation and condensation of water, as in drops of rain, as in tail after jet, as in clouds, fog, etc. Evaporations of water need energy. To evaporate 1 kg of water we need 539 kcal of energy. Every condensation of water released energy in the same amount. Evaporation of water is cooling surfaces, from which evaporation occur and air close to those surfaces. It is reasons, why in summer time is always cooler close to oceans, seas, lakes and rivers. We must pay attention, that only methane (CH4) is lighter than water vapor. Nitrous oxide (N2O), carbon dioxide (CO2), nitrogen (N2), oxygen (O2), are heavier than water vapor. It property of water vapor helps convection forces to mix air with height. Here it will be helpful to repeat, what offer to us Wikipedia: "The temperature falls with height precisely because most of the atmosphere is convecting, which leads to a fall of temperature with height because of pdV work.” Fall of temperature with height helps condense some water vapor and create water droplets. This process released heat, which increase temperature of surrounded gases. Hotter air recreate convection forces, which bring some of air higher, where again some of water vapor will condensed and released additional heat. It dynamic process of partially condensation with height will repeat many times till upper troposphere (around ten kilometers high), where so cold that 99% of water vapor will condensed to water droplets. It process helps all gases in air bring energy 10 km close to space, where energy will go to space easy, than from oceans level. Mankind activity not only reduces evaporation of water from continents by deforestation, tilling land, growing the same crop on huge area. Mankind activity decreased reflection of direct sun radiation, by soot, roads, homes, cities, etc. Mankind activity correlate with energy, which we use. Most of energy, used by mankind increased carbon dioxide, which is ease use as coefficient in climate models. In reality carbon dioxide is playing not so significant role in climate change, as reduction of evaporation on continents and decreasing reflection of direct sun radiation. Understanding these realities, create new possibilities in fighting climate change. It is economically difficult to change reflection of direct sun radiation. It is easy to increase evaporation of water on continents by forests. We only need to found economical reason to grow forests.

Wed, Sep 21, 2011 GNAC TEXAS

Your bias shows thru out the artical - assuming buring coal and the resulting CO2 are the source of warming. The energy of the sun hitting the earth each day is 8,000 time more than all the energy produced (coal, nuclear, hydro, wind, geothermal, etc.). Assuming all energy produced is ultimately "heat" in the enviroment - I fail to see how 1/8,000 th is having the impact. It is well documented that CO2 is a weak greenhouse gas compared to H2O, yet we MUST blame something - other than considering the output of the sun varies by more than 1/8,000 th.

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